A simplified conceptual model of the human cervical spine for evaluating force transmission in upright static posture

Abstract

Objective: To develop a simplified graphical model appropriate for the evaluation of proposed theoretical force transmission mechanisms in the upright static cervical spine. The model is used to demonstrate in a visual format the underlyingmechanical principles contributing to an optimal mechanical configuration of the cervical spine in upright posture. The model is also used to explore the relative mechanical efficiency of 2 different force transmission methods. Method: A graphical model was developed to illustrate relevant force vectors acting on the head and neck in upright posture. This model was used to calculate theoretical static loading on the structures of the neck under various loading conditions resulting from specific configurations of passive elements and active supportive muscle effort. Results: From the information gained from the model, a theorized optimal mechanical configuration and theorized role of various components of the cervical spine in static upright posture is presented. The model is used to test the mechanical validity of a concurrent force system with intersegmental muscle force rather than the parallel force system presented in the literature. The alternate models are examined in relation to their predictions and theoretical implications with respect to force transmission in the cervical spine. Conclusion: A simplified model has been developed that facilitates the graphical representation of forces involved in maintaining static upright posture in the human cervical spine. The model is used to explore the optimal spinal configuration of the major mechanical components of the neck. (J Manipulative Physiol Ther 2002;25:306-17)